This section presents the weekly calculation of the Effective Reproduction Number (Rt). The calculation is updated every week and is based on official reports of deaths and infections
For the Rt calculation, the first week is based on the first reported death and infection in each country. From there, each week is understood as the following 7 days.
Rt shows the weekly transmission rate of the virus. An Rt = 1 indicates that, during the week, the epidemic did not grow exponentially and stabilized; an Rt < 1 suggests that, during the week, the epidemic was in decline and under “control,” and an Rt > 1 suggests that, during the week, the epidemic had exponential growth and can be considered “out of control.” In the current pandemic, one must look to Rt to assess viral transmission. The goal is to obtain an Rt < 1 consistently, week after week, until the epidemic is over.
What is the difference between R0 and Rt? While R0 describes the potential for spread of an infection in a fully susceptible population, the effective reproductive number, or Rt, captures the rate of transmission once the virus has spread and as containment measures have begun.
See here for a more complete methodological explanation.
Our own graphic, based on data from Johns Hopkins University
Our own graphic, based on data from Johns Hopkins University
Our own graphic, based on data from Johns Hopkins University